How to Calculate How Much Decking You Need?

When you're planning a decking project, knowing how to calculate the right amount of material is essential. Whether you're managing procurement for a project, ordering in bulk for stock, or building multiple decks, an accurate estimate helps reduce waste, avoid shortage, and streamline installation.

This guide walks you through each step in a simple, professional way — suitable for WPC, composite, or timber decking systems.

1. Measure the Total Deck Area

Start by measuring the full surface where decking will be installed.

For rectangular decks:
 Use the standard formula:
 Area (m²) = Length × Width

Example:
 A 60 m × 40 m deck = 2400 m²

For irregular shapes:
 Divide the layout into smaller rectangles or triangles, calculate each section, and add them together.

Accurate area measurement is the foundation for every other calculation.

2. Check the Decking Board Specifications

Each decking product covers a certain surface area depending on its width, length, and joint gap. Refer to the manufacturer's specification — for instance, MATECO outdoor co-extrusion decking board J14021CD measures 140 mm × 21 mm.

Convert the dimensions into meters before calculation:
 140 mm = 0.14 m

If the board length is 2.4 m:
 Coverage per board = 0.14 m × 2.4 m = 0.336 m² (before accounting for gaps).

3. Calculate the Number of Boards

Now divide the total adjusted area by the coverage per board:

Number of boards = Total area ÷ Coverage per board

Example:
 400 m² ÷ 0.336 m² = 1191 boards
 That’s the quantity to order for this project.

4. Adjust for Special Deck Patterns

Not all decks are built with straight, parallel boards. Some layouts — such as diagonal or framed designs — require extra material due to additional cutting and alignment. Here's how to plan for those cases:

1) Straight or Parallel Layouts: Use the standard calculation. This layout is the most efficient and produces the least waste.

2) Diagonal (45°) Layouts: Add around 5–10% more decking boards. The angled placement increases offcuts along the edges.

3) Herringbone or Chevron Layouts: Add about 10% extra material. These designs require more precision cuts and result in greater waste.

4) Picture Frame or Border Designs: Calculate the border boards separately. These perimeter pieces often need miter cuts and do not follow the main deck pattern.

5) Multi-zone or Split-level Decks: Measure each section independently and total the results. This approach ensures you order enough material for all levels and transitions.

Adjusting your material estimate based on layout will help you avoid short supply and keep the installation process smooth and predictable.

5. Estimate Joists and Substructure

Decking needs proper support. The number of joists depends on deck's square footage.

1 square meter of decking requires approximately 3 meters of joists.

Example:
 If your deck is 400 square meters, you'll need around 1200 meters of joists.

Include perimeter framing and blocking if you’re installing stairs or borders.

6. Calculate Fasteners and Clips

Our keel installation is generally spaced 30 centimeters apart, and fasteners are typically one per board and one per joist. A simple ratio is 21 fasteners per square meter.

Example:
 Taking our 140 mm wide decking as an example, 400 square meters of decking would require approximately 8400 fasteners.

For MATECO systems, you can use:

• JAC01 nylon fixing clips for standard boards

Add an extra 3–5% fasteners for replacement and site losses.

7. Include Fascia and Edge Finishing

If the design includes fascia boards or edge trims, calculate the perimeter:

Perimeter (m) = 2 × (Length + Width)

Then divide by the fascia board length to determine how many you need. This ensures clean finishing and full material coverage.

Final Thoughts

By following these calculation steps, you can confidently determine how much decking material to order — whether for a small residential project or a large commercial platform. The method is precise, repeatable, and adaptable to any WPC or composite product line.

If you are looking for a WPC manufacturer, MATECO will be your best choice.
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    Email: info@matecowpc.com